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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v3aSt-00000005PQC-0J0y; Tue, 30 Sep 2025 13:32:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v3aSp-00000005POw-3f0A for linux-arm-kernel@lists.infradead.org; Tue, 30 Sep 2025 13:32:21 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0D4B4113E; Tue, 30 Sep 2025 06:32:09 -0700 (PDT) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CC9973F59E; Tue, 30 Sep 2025 06:32:12 -0700 (PDT) Message-ID: <7b13b1b5-295e-499b-9f8f-da168099377d@arm.com> Date: Tue, 30 Sep 2025 14:32:11 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 13/29] arm_mpam: Probe the hardware features resctrl supports To: James Morse , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org Cc: D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , fenghuay@nvidia.com, baisheng.gao@unisoc.com, Jonathan Cameron , Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-14-james.morse@arm.com> <8ed9fbe9-1075-4abb-91d0-20203906a4dc@arm.com> <32bc0e4a-d0bb-4aaa-8706-95a6edd470a9@arm.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <32bc0e4a-d0bb-4aaa-8706-95a6edd470a9@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250930_063220_031644_DD1A6749 X-CRM114-Status: GOOD ( 22.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi James, On 9/29/25 18:45, James Morse wrote: > Hi Ben, > > On 11/09/2025 16:37, Ben Horgan wrote: >> On 9/10/25 21:42, James Morse wrote: >>> Expand the probing support with the control and monitor types >>> we can use with resctrl. > >>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h >>> index 4cc44d4e21c4..5ae5d4eee8ec 100644 >>> --- a/drivers/resctrl/mpam_internal.h >>> +++ b/drivers/resctrl/mpam_internal.h >>> @@ -112,6 +112,55 @@ static inline void mpam_mon_sel_lock_init(struct mpam_msc *msc) >>> raw_spin_lock_init(&msc->_mon_sel_lock); >>> } >>> >>> +/* >>> + * When we compact the supported features, we don't care what they are. >>> + * Storing them as a bitmap makes life easy. >>> + */ >>> +typedef u16 mpam_features_t; >>> + >>> +/* Bits for mpam_features_t */ >>> +enum mpam_device_features { >>> + mpam_feat_ccap_part = 0, >>> + mpam_feat_cpor_part, >>> + mpam_feat_mbw_part, >>> + mpam_feat_mbw_min, >>> + mpam_feat_mbw_max, >>> + mpam_feat_mbw_prop, >>> + mpam_feat_msmon, >>> + mpam_feat_msmon_csu, >>> + mpam_feat_msmon_csu_capture, >>> + mpam_feat_msmon_csu_hw_nrdy, >>> + mpam_feat_msmon_mbwu, >>> + mpam_feat_msmon_mbwu_capture, >>> + mpam_feat_msmon_mbwu_rwbw, >>> + mpam_feat_msmon_mbwu_hw_nrdy, >>> + mpam_feat_msmon_capt, >>> + MPAM_FEATURE_LAST, >>> +}; > >> I added a garbled comment about this for v1. What I was trying to say is >> that I don't think this quite matches what resctrl supports. For >> instance, I don't think mpam_feat_ccap_part matches a resctrl feature. > > Ah - right. I thought you meant something was removed later. > Looks like I thought something could be emulated with CCAP, but that turns out not to be > true because it doesn't have an implicit isolation property, which the > resctrl:bitmap-from-userspace requires. > (I think rwbw was a later addition to the architecture and I added it to the wrong patch). > > I'll move that, _prop and _rwbw to the later patch. The split is fairly arbitrary - it was I think ccap gets split into finer grained features later on which seems fine. > just somewhere to split an otherwise large patch, and does help determine if a bug is > going to be visible to user-space or not. Ok, sensible, I hadn't appreciated the user-space visibility aspect. > > _capt can go completely. Last I heard no-one was interested in firmware descriptions of > how the capture hardware can be triggered. I suspect no-one has done anything with it. So, if I've understood correctly this leaves you with the following in this patch. mpam_feat_cpor_part, mpam_feat_mbw_part, mpam_feat_mbw_min, mpam_feat_mbw_max, mpam_feat_mbw_prop, mpam_feat_msmon, mpam_feat_msmon_csu, mpam_feat_msmon_csu_hw_nrdy, mpam_feat_msmon_mbwu, mpam_feat_msmon_mbwu_hw_nrdy, Looks like the correct, resctrl based, split. > > > Thanks, > > James Thanks, Ben